Homogeneous superchondritic <sup>142</sup>Nd/<sup>144</sup>Nd in the mid‐ocean ridge basalt and ocean island basalt mantle

Jackson, Matthew G.; Carlson, Richard W.

doi:10.1029/2012gc004114

Cited by 55 publications

(49 citation statements)

References 72 publications

(131 reference statements)

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“…treatment of their data using the methodology of this paper provides a similar value to that reported here. (2) The Sm/Nd ratio estimated for the MORB-source mantle and the mean 143 Nd/ 144 Nd of MORB (even when excluding segments within 500 km of hot spots) overlaps those estimated for the "non-chondritic primitive mantle" [e.g., Jackson and Carlson, 2012]. A MORBsource mantle that is equivalent to the non-chondritic primitive mantle creates serious mass-balance issues for the silicate Earth, since continent extraction would somehow not have led to mantle depletion.…”

Section: Discussionmentioning

confidence: 99%

“…Of course, 146 Sm is not the only radioactive isotope of Sm; 147 Sm also decays to 143 Nd. The increase in the EDR Sm/Nd ratio leads to a predicted 143 Nd/ 144 Nd for the "primitive mantle" or bulk silicate Earth of 0.5130 AE 0.0001 [Jackson and Carlson, 2012].…”

Section: K/u Ratiomentioning

confidence: 99%

“…Jackson and Carlson [2012] predict the isotopic range for "primitive mantle" to be between 0.5129 and 0.5131. The mean 143 Nd/ 144 Nd for ALL MORB (excluding back arcs, 0.513057AE0.000017) and ALL NORMAL MORB (0.513072AE0.000018) fall within this range.…”

Section: K/u Ratiomentioning

confidence: 99%

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The mean composition of ocean ridge basalts

Gale

Dalton

Langmuir

et al. 2013

Geochem. Geophys. Geosyst.

142

317

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[1] The mean composition of mid-ocean ridge basalts (MORB) is determined using a global data set of major elements, trace elements, and isotopes compiled from new and previously published data. A global catalog of 771 ridge segments, including their mean depth, length, and spreading rate enables calculation of average compositions for each segment. Segment averages allow weighting by segment length and spreading rate and reduce the bias introduced by uneven sampling. A bootstrapping statistical technique provides rigorous error estimates. Based on the characteristics of the data, we suggest a revised nomenclature for MORB. "ALL MORB" is the total composition of the crust apart from back-arc basins, N-MORB the most likely basalt composition encountered along the ridge >500 km from hot spots, and D-MORB the depleted end-member. ALL MORB and N-MORB are substantially more enriched than early estimates of normal ridge basalts. The mean composition of back-arc spreading centers requires higher extents of melting and greater concentrations of fluid-mobile elements, reflecting the influence of water on back-arc petrogenesis. The average data permit a re-evaluation of several problems of global geochemistry. The K/U ratio reported here (12,340 AE 840) is in accord with previous estimates, much lower than the estimate of Arevalo et al. (2009). The low Sm/Nd and 143 Nd/ 144 Nd ratio of ALL MORB and N-MORB provide constraints on the hypothesis that Earth has a non-chondritic primitive mantle. Either Earth is chondritic in Sm/Nd and the hypothesis is incorrect or MORB preferentially sample an enriched reservoir, requiring a large depleted reservoir in the deep mantle.

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Section: Discussionmentioning

confidence: 99%

Section: K/u Ratiomentioning

confidence: 99%

See 1 more Smart Citation

The mean composition of ocean ridge basalts

Gale

Dalton

Langmuir

et al. 2013

Geochem. Geophys. Geosyst.

142

317

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“…[6] Here we explore the implications for Nd in all modern terrestrial mantle reservoirs requires that they descend from a parental reservoir that has a Sm/Nd ratio $4.5-7.9% higher than chondrites [e.g., Jackson and Carlson, 2012] Nd as the terrestrial standard [e.g., Boyet and Carlson, 2006;Caro et al, 2006;Andreasen et al, 2008;Murphy et al, 2010;Jackson and Carlson, 2012]. There is no observational evidence from geochemistry for an EER, but its existence cannot be excluded.…”

mentioning

confidence: 99%

Major and trace element composition of the high ³He/⁴He mantle: Implications for the composition of a nonchonditic Earth

Jackson

Jellinek

2013

Geochem Geophys Geosyst

Self Cite

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[1] The bulk composition of the silicate portion of the Earth (BSE) has long been assumed to be tied to chondrites, in which refractory, lithophile elements like Sm and Nd exist in chondritic relative abundances. However, the Nd from 0.51263 (chondritic) to 0.51300. The new BSE composition is depleted in highly incompatible elements, including K, relative to the chondrite-based BSE, and offers a solution the ''missing '' 40 Ar paradox. This BSE compositional model requires that >83% of the mantle is depleted to form continental crust. It also implies a $30% reduction in BSE U, Th and K, and therefore in the current rate of radiogenic heating and, thus, a proportional increase in the heat flow delivered to surface by plate tectonics. We explore thermal history models including effects related to a newly recognized evolution in the style of plate tectonics over Earth history: The lower radiogenic heat production may delay the onset of core convection and dynamo action to as late as 3.5 Gyr.

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“…Guitreau et al [64] also discussed the possibility that a mantle source of this type produced 142 Nd/ 144 Nd variation within early Archaean lavas from Québec. Jackson & Carlson [56] point out that partial crystallization of the mantle in the early Hadean could have formed 'hidden' low-Sm/Nd reservoirs, leaving the rest of the mantle with Sm/Nd approximately 6% higher than the probable meteorite source of the Earth. Alternatively, they suggest that the Earth may not have accreted the model meteorite composition.…”

Section: (C) Freezing Of Deep Mantlementioning

confidence: 99%

Terrestrial aftermath of the Moon-forming impact

Sleep

Zahnle

Lupu

2014

Phil. Trans. R. Soc. A.

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Much of the Earth's mantle was melted in the Moon-forming impact. Gases that were not partially soluble in the melt, such as water and CO 2 , formed a thick, deep atmosphere surrounding the post-impact Earth. This atmosphere was opaque to thermal radiation, allowing heat to escape to space only at the runaway greenhouse threshold of approximately 100 W m −2 . The duration of this runaway greenhouse stage was limited to approximately 10 Myr by the internal energy and tidal heating, ending with a partially crystalline uppermost mantle and a solid deep mantle. At this point, the crust was able to cool efficiently and solidified at the surface. After the condensation of the water ocean, approximately 100 bar of CO 2 remained in the atmosphere, creating a solar-heated greenhouse, while the surface cooled to approximately 500 K. Almost all this CO 2 had to be sequestered by subduction into the mantle by 3.8 Ga, when the geological record indicates the presence of life and hence a habitable environment. The deep CO 2 sequestration into the mantle could be explained by a rapid subduction of the old oceanic crust, such that the top of the crust would remain cold and retain its CO 2 . Kinematically, these episodes would be required to have both fast subduction (and hence seafloor spreading) and old crust. Hadean oceanic crust that formed from hot mantle would have been thicker than modern crust, and therefore only old crust underlain by cool mantle lithosphere could subduct. Once subduction started, the basaltic crust would turn into dense eclogite, increasing the rate of subduction. The rapid subduction would stop when the young partially frozen crust from the rapidly spreading ridge entered the subduction zone.

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Homogeneous superchondritic ¹⁴²Nd/¹⁴⁴Nd in the mid‐ocean ridge basalt and ocean island basalt mantle

Cited by 55 publications

References 72 publications

The mean composition of ocean ridge basalts

The mean composition of ocean ridge basalts

Major and trace element composition of the high ³He/⁴He mantle: Implications for the composition of a nonchonditic Earth

Terrestrial aftermath of the Moon-forming impact

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Homogeneous superchondritic 142Nd/144Nd in the mid‐ocean ridge basalt and ocean island basalt mantle

Cited by 55 publications

References 72 publications

The mean composition of ocean ridge basalts

The mean composition of ocean ridge basalts

Major and trace element composition of the high 3He/4He mantle: Implications for the composition of a nonchonditic Earth

Terrestrial aftermath of the Moon-forming impact

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Homogeneous superchondritic ¹⁴²Nd/¹⁴⁴Nd in the mid‐ocean ridge basalt and ocean island basalt mantle

Major and trace element composition of the high ³He/⁴He mantle: Implications for the composition of a nonchonditic Earth